Kokas Márton, Budai András, Kádár Andrea, Mozaffaritabar Soroosh, Zhou Lei, Téglás Tímea, Orova Rebeka Sára, Gáspár Dániel, Németh Kristóf, Toth Daniel Marton, Sayour Nabil V, Kovácsházi Csenger, Xue Andrea, Szatmári Réka Zsuzsanna, Törőcsik Beáta, Máthé Domokos, Kovács Noémi, Szigeti Krisztián, Nagy Péter, Szatmári Ildikó, Fekete Csaba, Arányi Tamás, Varga Zoltán V, Ferdinandy Péter, Radák Zsolt, Kozlov Andrey V, Tretter László, Komlódi Tímea, Ambrus Attila
Department of Biochemistry, Semmelweis University, 37-47 Tuzolto Street, Budapest, 1094, Hungary.
Department of Pathology, Forensic and Insurance Medicine, Semmelweis University, 93 Ulloi Street, Budapest, 1091, Hungary.
Redox Biol. 2025 Jun 27;85:103743. doi: 10.1016/j.redox.2025.103743.
The alpha-ketoglutarate dehydrogenase complex (KGDHc), also known as the 2-oxoglutarate dehydrogenase complex, plays a crucial role in oxidative metabolism. It catalyzes a key step in the tricarboxylic acid (TCA) cycle, producing NADH (primarily for oxidative phosphorylation) and succinyl-CoA (for substrate-level phosphorylation, among others). Additionally, KGDHc is also capable of generating reactive oxygen species, which contribute to mitochondrial oxidative stress. Hence, the KGDHc and its dysfunction are implicated in various pathological conditions, including selected neurodegenerative diseases. The pathological roles of KGDHc in these diseases are generally still obscure. The aim of this study was to assess whether the mitochondrial malfunctions observed in the dihydrolipoamide succinyltransferase (DLST) and dihydrolipoamide dehydrogenase (DLD) double-heterozygous knockout (DLSTDLD, DKO) mice are associated with neuronal and/or metabolic abnormalities. In the DKO animals, the mitochondrial O consumption and ATP production rates both decreased in a substrate-specific manner. Reduced HO production was also observed, either due to Complex I inhibition with α-ketoglutarate or reverse electron transfer with succinate, which is significant in ischaemia-reperfusion injury. Middle-aged DKO mice exhibited minor cognitive decline, associated with microgliosis in the cerebral cortex and neuronal death in the Cornu Ammonis subfield 1 (CA1) of the hippocampus, indicating neuroinflammation. This was supported by increased levels of dynamin-related protein 1 (Drp1) and reduced levels of mitofusin 2 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in DKO mice. Observations on activity, food and oxygen consumption, and blood amino acid and acylcarnitine profiles revealed no significant differences. However, middle-aged DKO animals showed decreased performance in the treadmill fatigue-endurance test as compared to wild-type animals, accompanied by subtle resting cardiac impairment, but not skeletal muscle fibrosis. In conclusion, DKO animals compensate well the double-heterozygous knockout condition at the whole-body level with no major phenotypic changes under resting physiological conditions. However, under high energy demand, middle-aged DKO mice exhibited reduced performance, suggesting a decline in metabolic compensation. Additionally, microgliosis, neuronal death, decreased mitochondrial biogenesis, and altered mitochondrial dynamics were observed in DKO animals, resulting in minor cognitive decline. This is the first study to highlight the in vivo changes of this combined genetic modification. It demonstrates that unlike single knockout rodents, double knockout mice exhibit phenotypical alterations that worsen under stress situations.
α-酮戊二酸脱氢酶复合体（KGDHc），也被称为2-氧代戊二酸脱氢酶复合体，在氧化代谢中起着至关重要的作用。它催化三羧酸（TCA）循环中的关键一步，产生NADH（主要用于氧化磷酸化）和琥珀酰辅酶A（用于底物水平磷酸化等）。此外，KGDHc还能够产生活性氧，这会导致线粒体氧化应激。因此，KGDHc及其功能障碍与多种病理状况有关，包括某些神经退行性疾病。KGDHc在这些疾病中的病理作用通常仍不清楚。本研究的目的是评估在二氢硫辛酰胺琥珀酰转移酶（DLST）和二氢硫辛酰胺脱氢酶（DLD）双杂合敲除（DLSTDLD，DKO）小鼠中观察到的线粒体功能障碍是否与神经元和/或代谢异常有关。在DKO动物中，线粒体的氧气消耗和ATP产生速率均以底物特异性方式降低。还观察到由于α-酮戊二酸对复合体I的抑制或琥珀酸的逆向电子传递导致的HO产生减少，这在缺血再灌注损伤中很重要。中年DKO小鼠表现出轻微的认知能力下降，与大脑皮层的小胶质细胞增生和海马体角回1区（CA1）的神经元死亡有关，表明存在神经炎症。DKO小鼠中动力相关蛋白1（Drp1）水平升高以及线粒体融合蛋白2和过氧化物酶体增殖物激活受体γ共激活因子1α（PGC-1α）水平降低支持了这一点。对活动、食物和氧气消耗以及血液氨基酸和酰基肉碱谱的观察没有发现显著差异。然而，与野生型动物相比，中年DKO动物在跑步机疲劳耐力测试中的表现下降，伴有轻微的静息性心脏损伤，但没有骨骼肌纤维化。总之，DKO动物在静息生理条件下在全身水平上能很好地补偿双杂合敲除状态，没有明显的表型变化。然而，在高能量需求下，中年DKO小鼠表现出性能下降，表明代谢补偿能力下降。此外，在DKO动物中观察到小胶质细胞增生、神经元死亡、线粒体生物发生减少和线粒体动力学改变，导致轻微的认知能力下降。这是第一项突出这种联合基因修饰体内变化的研究。它表明与单敲除啮齿动物不同，双敲除小鼠表现出在应激情况下会恶化的表型改变。
